Final answer:
The answer is c. FAD and NAD are coenzymes in biochemical reactions, specifically serving as electron carriers in redox reactions essential for ATP production. They are not catalysts, substrates, or inhibitors.
Step-by-step explanation:
FAD (Flavin Adenine Dinucleotide) and NAD (Nicotinamide Adenine Dinucleotide) are coenzymes that act as electron carriers in biochemical reactions. They play a critical role in oxidation-reduction (redox) reactions, where they accept electrons and protons to become FADH2 and NADH, respectively. This process is vital for the transfer of energy during the creation of ATP (Adenosine Triphosphate), the energy currency of the cell. Although they are crucial for these reactions, they are not catalysts, substrates, or inhibitors; instead, they facilitate the reaction by serving as electron carriers.
They accept hydrogen atoms and electrons from substrates, and get converted to their reduced forms, FADH2 and NADH, respectively. These reduced coenzymes then transfer the electrons to other molecules, such as ATP, during the process of oxidative phosphorylation in cellular respiration.